Condensed Financial Information (Parent Company Only) - Condensed Balance Sheets (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Condensed balance sheets:
Cash and cash equivalents	$ 801,332,000	$ 472,447,000
Investment in subsidiaries, at equity:
Other assets	62,953,000	68,177,000
Total assets	7,721,761,000	7,325,527,000
Preferred stock pending redemption	50,000,000	0
Subordinated debentures held by subsidiary trusts	82,477,000	123,715,000
Total liabilities	6,970,575,000	6,554,507,000
Stockholders’ equity	751,186,000	771,020,000	736,802,000	574,434,000
Total liabilities and stockholders’ equity	7,721,761,000	7,325,527,000
Parent Company
Condensed balance sheets:
Cash and cash equivalents	95,407,000	131,860,000
Investment in subsidiaries, at equity:
Equity method investments	804,239,000	778,322,000
Advances from subsidiaries, net	697,000	0
Other assets	25,815,000	26,246,000
Total assets	926,158,000	936,428,000
Other liabilities	22,495,000	19,552,000
Advances to subsidiaries, net	0	2,141,000
Long-term debt	20,000,000	20,000,000
Preferred stock pending redemption	50,000,000	0
Subordinated debentures held by subsidiary trusts	82,477,000	123,715,000
Total liabilities	174,972,000	165,408,000
Stockholders’ equity	751,186,000	771,020,000
Total liabilities and stockholders’ equity	926,158,000	936,428,000
Bank subsidiary
Investment in subsidiaries, at equity:
Equity method investments	802,270,000	776,349,000
Nonbank subsidiaries
Investment in subsidiaries, at equity:
Equity method investments	$ 1,969,000	$ 1,973,000